Administrator Guide

Creating an Output QoS Policy
To create an output QoS policy, use the following commands.
1. Create an output QoS policy.
CONFIGURATION mode
qos-policy-output
2. After you congure an output QoS policy, do one or more of the following:
Conguring Policy-Based Rate Shaping
Allocating Bandwidth to Queue
Congure a Scheduler to Queue
Specifying WRED Drop Precedence
Conguring Policy-Based Rate Shaping
To congure policy-based rate shaping, use the following command.
• Congure rate shape egress trac.
QOS-POLICY-OUT mode
rate-shape
Allocating Bandwidth to Queue
The Dell Networking recommends pre-calculating your bandwidth requirements before creating them. Make sure you apply the QoS
policy to all the four queues and that the sum of the bandwidths allocated through them is exactly 100.
When you apply the QoS policies through output policy map and if the sum of the bandwidth percentages congured is below or
above 100, the actual bandwidth is allocated proportionally. If the sum of allocated bandwidth is less than 100, the unused bandwidth
is allotted to un-allocated queues. If the sums of allocated bandwidth exceed 100, then 1% of the bandwidth is derived for
unassigned queues from assigned queues.
• Allocate bandwidth to queues.
QOS-POLICY-OUT mode
bandwidth-percentage
Congure a Scheduler to Queue
By default, the MXL switch schedules packets for egress based on weighted round robin (WRR).
NOTE: The bandwidth and scheduler cannot be congured at the same time. Policy-level scheduler assigned to queue is
applied to both unicast and multicast trac.
Setting DSCP Values for Egress Packets Based on Flow
Match-any Layer 3 ows may have several match criteria. All ows that match at least one of the match criteria are mapped to the
same queue because they are in the same class map.
Setting a DSCP value from QOS-POLICY-IN mode (refer to Setting a DSCP Value for Egress Packets) assigns the same DSCP value
to all of the matching ows in the class-map.
The ow-based DSCP marking feature allows you to assign dierent DSCP to each match criteria.
• Create matching ows within a class map that have dierent DSCP values.
CLASS MAP mode
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Quality of Service (QoS)